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historic use of water within each river basin to detennine water which would be physically available in the various river sections. The Board staff took the results of the 1994 LRCWE study and applied the results to the 15 Mile Reach of the Colorado River mainstem, from the Grand Valley Irrigation Company's (GVIC) headgate to the confluence of the Gunnison River and Colorado River. This memorandum presents the results of the 1994 LRCWE study and additional data for the 15 Mile Reach of the Colorado River mainstem. LRCWE Study Approach The following are the major activities performed by LRCWE as part of their 1994 Physical Water Availability study: . Evaluated the study period of 1970-1992 to determine if it was representative of the complete period of use. . Reviewed USGS gaging station records for their appropriateness in characterizing the streamflows within stream reaches of interest. . Statistically generated gage records to fill incomplete gage records from the study period. . Adjusted gage records to account for major changes of water use in the basins during the study period ( The purpose of these adjustments was to bring gage station records during the period to an estimated 1992 level of depletion). . Presented statistical gage and adjusted gage record results in tabular and graphical formats on an annual, monthly, and daily basis. Study Period Statistical comparisons were made on an annual basis using gage flows, major reservoir operations and transbasin depletions. The 1970-1992 study period was evaluated to detennine whether or not this period was representative of the 1906-1992 period of record. The 1970-1972 period was selected for the following reasons: . The study period averages for the individual basins are within plus or minus six percent of the longer period averages. . The variability about the mean is greater for this study period, which provides the opportunity to evaluate wet and dry years that are typically greater in magnitude than the years outside of the study period. . The study period contains a mix of wet, dry and average years in the first part of the period, followed by an extended wet period in the early 1980's. The wet period is 3